over-tall plum tree
 

Hi,

I've just acquired a Marjorie's Seedling plum which, to judge by the
look of it, wasn't feathered in its first or second year as it ought to
have been, so it's now a single main stem --about 2cm in diameter-- with
some small twiggy branching at about five feet.

The question is, how should I prune it? If I were to cut the main stem
at about three feet, would it survive? Or is it --to judge by the
thickness of the stem-- too old for that treatment?

Any advice welcomed.

Brian Mitchell